javascript - How to register Polymer behavior with ES6? -

if

polymer({     is: 'pp-app',     behaviors: [playplan.helperbehavior],     scrollpagetotop() {       document.getelementbyid('maincontainer').scrolltop = 0;     },      ondatarouteclick() {       var drawerpanel = document.queryselector('#paperdrawerpanel');       if (drawerpanel.narrow) {         drawerpanel.closedrawer();       }     }   }); 

the behavior here works fine, in es6

  class playplanapp {     beforeregister() {       this.is = 'pp-app';       this.properties = {};       this.behaviors = [playplan.helperbehavior];     }      scrollpagetotop() {       document.getelementbyid('maincontainer').scrolltop = 0;     }      ondatarouteclick() {       var drawerpanel = document.queryselector('#paperdrawerpanel');       if (drawerpanel.narrow) {         drawerpanel.closedrawer();       }     }   }   polymer(playplanapp); 

the behavior not works, how specify behaviors when using es6 ?

this caused

registercallback: function() {       // todo(sjmiles): perhaps method should called polymer-bootstrap?       this._desugarbehaviors(); // abstract       this._dobehavior('beforeregister'); // abstract       this._registerfeatures();  // abstract       this._dobehavior('registered'); // abstract     } 

_dobehavior('beforeregister') after _desugarbehaviors, here work around:

get behaviors() {       return [playplan.helperbehavior];     } 

btw, not work, because constructor never called(commented in polymer.base)

constructor() {       return [playplan.helperbehavior];     }